Identify the hardware vendor associated with a MAC address OUI prefix.
The first 24 bits (3 bytes) of a MAC address form the Organizationally Unique Identifier (OUI), assigned by IEEE to hardware manufacturers. Looking up the OUI reveals the device's manufacturer. The two least-significant bits of the first byte indicate whether the address is unicast/multicast and universal/local.
OUI extraction
OUI = first 3 bytes (6 hex digits) of the MAC address
A locally administered address (U/L bit set) means the MAC was assigned by software rather than burned into hardware by the manufacturer — common for virtual machines, privacy-randomized mobile devices, and software-defined networking. The OUI won't identify a real hardware vendor in this case.
IEEE maintains the authoritative OUI registry at standards.ieee.org/products-programs/regauth. It contains over 30,000 registered OUIs. This calculator uses a common subset for offline identification.